The absence of sensitivity changes of the rabbit oviduct to phenylephrine and isoproterenol during early gestation.

The response of the rabbit perfused oviduct in vivo to phenylephrine (PE), isoproterenol (ISO) and epinephrine (EPI) was studied to determine if a purported change from alpha-adrenergic receptor dominance to beta-adrenergic receptor dominance during early gestation occurs (i.e. prior to implantation). The response of the tissue to PE did not change during early gestation, even in the presence of beta-receptor blockade by propranolol. The response to ISO of the PE-stimulated oviduct also did not change. However, the dose-response curve to EPI was shifted horizontally to the right 4 days after mating suggesting a tissue desensitization. It was concluded that the decreased oviductal sensitivity to EPI observed during early gestation could not be attributed to a change from alpha-receptor dominance to beta-receptor dominance.